The present invention relates to field emitter electron sources for use in ultra-high vacuum (UHV) and extremely high vacuum (XHV) instrumentation, and more particularly to diamond based such emitters.
Present day Ultra High Vacuum and Extremely High Vacuum instrumentation is based primarily on thermoionic electron sources. These sources operate at very high temperatures and consequently, tend to desorb gases from the walls of the vacuum chamber and instrumentation thereby affecting the pressure one is trying to measure. Additionally, at the normal operating current of about 1 mA, they also affect the pressure measurement due to electron stimulated desorption of gases from the vacuum walls as well as the elements of the instruments.
Several attempts have been made to substitute field emitter array cold electron sources for the thermoionic electron sources. However, these field emitters have relatively large surface areas and create problems due to continuous outgassing.
Cold-cathode electron field emitters using diamonds have been suggested in the prior art because of the negative electron affinity of their surfaces, but these emitters are generally based on thin films of diamonds (less than about 5xcexc) or alternatively, thin layers of diamond particles embedded in a coating material. While these have often provided improved emitters, the density of their emission fields is often hard to control and not sufficient to provide optimum performance for vacuum instrumentation. Additionally, in the case of bonded diamond particles, the coating is a source of additional measurement interference.
According to the present invention there is provided a xe2x80x9csolidxe2x80x9d diamond i.e. greater than 5xcexc thick, electron emitter that has been xe2x80x9cmachinedxe2x80x9d using non-contact techniques to a point having a radius of less than about 100xcexc, preferably below about 10xcexc, and most preferably between about 3 tenths of an angstrom and about 3xcexc. The solid diamond electron emitters of the present invention can perform, even at these small radii, as multi-point emitters depending upon the radius and roughness of the pointed tip. The emitters of the present invention can be used in arrays of individual emitters to obtain relatively large area emitter fields for applications where such fields are necessary. Production of the solid diamond emitters of the present invention is preferably accomplished using non-contact electron or ion beam or laser machining techniques.
Residual gas analyzers (RGA), field emitter extractor gauge analyzers (FERGA), Faraday cup detectors and other high and ultra high vacuum devices utilizing the solid diamond emitters of the present invention as well as free electron lasers and Linacs that use the technology described herein are also possible.